Anchor chains for marine use can be connected using known designs of shackles. Shackles usually comprises at least two portions, each of which will usually connect with a respective link on separate chains or with a link on a chain and an anchor, before the two shackle portions are connected together to join the chains or the chain to the anchor. The shackle should preferably be capable of withstanding the same forces as the chain links, but this is often a difficult compromise for the multipart shackle and frequent inspections are needed to assess the condition of the shackles, which is costly and inconvenient.
There are many different styles of shackles, swivels and connecting links. The two main types of connecting links (chain or anchor) in use are Kenter style links or “Baldt” style links. The difference between the two is in the design of the way the links open and close. The Kenter link consists of two opposite halves that slide together. The Baldt link has a C-shaped body and uses two caps to connect the open end of the C together.
U.S. Pat. No. 5,983,620 to Amoss discloses a “Kenter” type detachable connecting link without button shoulders that shows no apparent loss of strength compared to one with button shoulders. Versatility, however, is increased, enabling one link to fit several chain sizes, instead of just one. Preferably the button is aligned with the link cross section.
French Patent 2 581 150 to Caron discloses two identical half-links with a male end and a female end. The two half-links form, by mutual interlocking, a link locked by a locking component. Each male end comprises a bearing surface composed of several staged elementary bearing surfaces. The invention applies to chains for boats and oil platforms.
WO 2007/068472 to Feuerstein discloses a connector, particularly to a shackle suitable for use in connecting two links of a chain, more particularly to a connector comprising a first portion and a second portion, at least one first connector arm on the first portion and at least one second connector arm on the second portion, wherein both the first and second connector arms have at least one bearing surface and are able to engage one another when the connector is coupled by means of the bearing surfaces.
However, none of the prior art connectors meet the new offshore standards established in 2009 by DNV-OS-E302. There are many classification societies such as ABS (American Bureau of Shipping), Lloyds, BV (Bureau Veritas), DNV (Det Norske Veritas), etc. that examine links and supervise the testing before certifying its use for a vessel or mooring setup under their classification. According to the new DNV standard, the breaking load (kN) of a grade R5 connector is 0.0320 d2(44−0.08 d) (wherein d is the chain nominal diameter). Therefore, for example, the breaking load for a 76 mm shackle should be about 7009 kN under the new DNV standard. However, typical 76 mm shackles, regardless of the configuration have a break load of 6001 kN, which is well below the new DNV standards. Accordingly, there remains a need for a shackle that can meet the new DNV standards.